Manufactured buildings, such as manufactured or mobile homes and offices, are manufactured remote from an instillation site and moved on wheels to the installation site. The manufactured building typically includes long, longitudinal support beams underneath the building to support the floor of the building. During typical installation, a plurality of piers placed between a ground pan and the support beam support the building level on the site. Installed manufactured buildings also are connected to foundation systems to resist lateral and longitudinally wind forces on the building. These foundation systems use a ground pan and an elongated strut connected at a lower end to the ground pan and at the upper end to a support beam of the manufactured building. The elongated strut can be oriented parallel to a longitudinal axis of the support beam or extend laterally from underneath one support beam to connect to the adjacent support beam of the manufactured buildings. Such foundations provide resistance to wind forces in both the lateral and longitudinal directions.
While these foundation assemblies have been successful in resisting wind loads on installed manufactured buildings, there are drawbacks to usage of these foundations in regions of the country in which the ground experiences frost heave. Heave in soil occurs when the water in the ground freezes. The freezing water expands, and causes the ground to heave up or rise up or swell. Frost heave causes the foundation ground pans (or pads) to move. This movement is communicated to the house through the enlongated struts between the ground pan and the support beam, and may contribute to the house becoming out of level. A building that is not level can result in openings in the building becoming out of skew. This causes doors to become skewed and not open or close properly such as in doorways and cabinetry. Windows likewise become difficult to open and close.
It is believed that there are three factors that contribute to frost heave. These factors are the soil being sufficiently saturated with water, the atmospheric temperature, and the duration of the saturation and cold temperatures. Efforts to resist frost heave have been made. Typically in areas that experience significant frost heave, the foundation must be engineered and extend below the frost line. This requires excavation of an in-ground footing and installation of a rigid or engineered foundation such as concrete footers and pilings. In other areas, skirting attaches around the perimeter of the manufactured home. The skirting extends from a lower edge of the manufactured home to the ground. The skirting encloses the space between the ground and the bottom of the manufactured home. The skirting also prevents flow of air under the home. Skirting used on the perimeter of manufactured buildings placed at sites with pier supports is not entirely successful in reducing or eliminating frost heave. Even with skirting, manufactured buildings placed at sites with pier supports and not engineered foundations, are susceptible to frost heave of the ground below the ground pan.
Accordingly, there is a need for an improved ground pan to support piers and foundation of manufactured buildings while resisting frost heave. It is to such that the present invention is directed.